Add support for char[N] as a histogram key

Signed-off-by: Brenden Blanco <bblanco@plumgrid.com>

src/cc/frontends/clang/b_frontend_action.cc

@@ -70,6 +70,8 @@ bool BMapDeclVisitor::VisitRecordDecl(RecordDecl *D) {
       result_ += "\"" + F->getName().str() + "\", \"unsigned long long\"";
     else
       TraverseDecl(F);
+    if (const ConstantArrayType *T = dyn_cast<ConstantArrayType>(F->getType()))
+      result_ += ", [" + T->getSize().toString(10, false) + "]";
     if (F->isBitField())
       result_ += ", " + to_string(F->getBitWidthValue(C));
     result_ += "], ";

src/python/bcc/__init__.py

@@ -256,7 +256,7 @@ class BPF(object):
                     slot = getattr(k, f2)
                     vals[slot] = v.value
                 for bucket, vals in tmp.items():
-                    print("\nBucket %s = %x" % (bucket_type, bucket))
+                    print("\nBucket %s = %r" % (bucket_type, bucket))
                     self._print_log2_hist(vals, val_type, 0)
             else:
                 vals = [0] * 65
@@ -429,7 +429,6 @@ class BPF(object):
         u"_Bool": ct.c_bool,
         u"char": ct.c_char,
         u"wchar_t": ct.c_wchar,
-        u"char": ct.c_byte,
         u"unsigned char": ct.c_ubyte,
         u"short": ct.c_short,
         u"unsigned short": ct.c_ushort,
@@ -452,7 +451,10 @@ class BPF(object):
             if len(t) == 2:
                 fields.append((t[0], BPF._decode_table_type(t[1])))
             elif len(t) == 3:
-                fields.append((t[0], BPF._decode_table_type(t[1]), t[2]))
+                if isinstance(t[2], list):
+                    fields.append((t[0], BPF._decode_table_type(t[1]) * t[2][0]))
+                else:
+                    fields.append((t[0], BPF._decode_table_type(t[1]), t[2]))
             else:
                 raise Exception("Failed to decode type %s" % str(t))
         cls = type(str(desc[0]), (ct.Structure,), dict(_fields_=fields))

tests/cc/test_histogram.py

@@ -5,10 +5,11 @@
 from bcc import BPF
 from ctypes import c_int, c_ulonglong
 import random
+import time
 from unittest import main, TestCase
 
 class TestHistogram(TestCase):
-    def _test_simple(self):
+    def test_simple(self):
         b = BPF(text="""
 #include <uapi/linux/ptrace.h>
 #include <linux/bpf.h>
@@ -52,6 +53,22 @@ int kprobe__htab_map_delete_elem(struct pt_regs *ctx, struct bpf_map *map, u64 *
                 except: pass
         b["hist1"].print_log2_hist()
 
+    def test_chars(self):
+        b = BPF(text="""
+#include <uapi/linux/ptrace.h>
+#include <linux/sched.h>
+typedef struct { char name[TASK_COMM_LEN]; u64 slot; } Key;
+BPF_HISTOGRAM(hist1, Key, 1024);
+int kprobe__finish_task_switch(struct pt_regs *ctx, struct task_struct *prev) {
+    Key k = {.slot = bpf_log2l(prev->real_start_time)};
+    if (!bpf_get_current_comm(&k.name, sizeof(k.name)))
+        hist1.increment(k);
+    return 0;
+}
+""")
+        for i in range(0, 100): time.sleep(0.01)
+        b["hist1"].print_log2_hist()
+
 
 if __name__ == "__main__":
     main()